header {
  /* 1vw表示屏幕宽度的1% */
  width: 100vw;
  /* 1vh表示屏幕高度的1% */
  height: 10vh;
  background-color: aqua;
}

main {
  width: 100vw;
  height: 90vh;
  display: flex;
}

.left {
  width: 30vw;
  height: 90vh;
  background-color: blue;
}

.center {
  width: 40vw;
  height: 90vh;
  background-color: lawngreen;
}

.right {
  width: 30vw;
  height: 90vh;
  background-color: lightcoral;
}
